The invention relates to a dispenser for dispensing a viscous fluid, to a package and to a method to dispense a viscous fluid. More particularly, the invention relates to dispensing a room-temperature vulcanizable (RTV) silicone rubber composition and more particularly a one component room temperature vulcanizable silicone rubber composition.
A one component RTV composition can comprise a silanol end-stopped diorganopolysiloxane polymer having a viscosity varying anywhere from 500 to 500,000 centipoise at 25° C. where an organic group of the polymer is a monovalent hydracarbon radical such as methyl or phenyl. A one-part RTV polyorganosiloxane composition that cures at room temperature to form an elastomer is widely used as an elastic gasket or sealant, adhesive or coating agent in electrical, electronic and construction industries. The RTV composition can comprise the silanol terminated polydiorganosiloxane and a cross-linking agent having more than two hydrolyzable groups per molecule. In a typical system, the crosslinking agent is methyltriacetoxy silane. When exposed to atmospheric moisture, the composition will begin to cure to form a skin in 10 to 20 minutes. The composition fully cures to a silicone elastomer in about 24 hours.
A one-part RTV composition can be formulated to have high temperature stability and weatherability characteristics. The composition can also be formulated to have enhanced resistance to oil swell. This composition is especially suitable as a gasketing composition or as a composition for formed-in placed gaskets, for example in automobiles.
In one application, an RTV composition can be used to seal sections of blocks or panels in construction, particularly in the construction of large buildings, such as high-rises. In construction, prefabricated sections or panels are brought together to a prescribed proximity that allows for expansion, contraction or for an expansion joint. Concrete blocks or panels are fabricated next to each other with a typical crevice distance of anywhere from ¼″ to 11/2″ or more in width. Accordingly, it is necessary to seal the block or panel joints with an elastomer to complete construction and to allow for expansion and contraction.
A block or panel sealing operation is carried out by inserting a filler material into the crevice and applying a sealant over the filler material. The sealant cures in place to form the seal. Several devices are known for applying sealant. For example, Santefort, U.S. Pat. No. 5,217,144 shows a collapsible tube to dispense highly viscous materials such as silicone gasket RTV composition. The tube is used as part of a dispenser that includes two engaging plates for squeezing the sides of the tube to cause the tube contents to be expressed from an open end. The dispenser also includes two handles to be gripped by a workman in applying the RTV composition. Kruazona, U.S. Pat. No. 4,295,439 and Kruazona, U.S. Pat. No. 4,295,439 show devices that include a roller structure for use with a tube to apply RTV composition.
Oftentimes, the crevice is situated at a difficult to access location or angle. For example, the crevice forming blocks or panels may be situated high on a building facade where it is dangerous to take a known caulk gun or dispensing device that has flaring parts or obstructing parts. Other construction features may limit or obstruct access to the crevice or the crevice forming panels themselves may be located with respect to one another in a manner that permits only a sharp angle access to the crevice. Oftentimes, a workman must hold on to a support while situating himself so that he can put down an accurate bead of sealant. However, known dispensers for viscous materials such as RTV gasket sealant are difficult to use and do not permit dispensing uniform narrow beads that are required to provide quick forming, complete seals of structures that are placed in awkward, hard to reach obstructed locations.
There is a need for an economical and inexpensive device for accurately applying a silicone RTV composition to seal a crevice. Also, there is a need for a collapsible tube dispenser that can be operated with only one hand for use in cramped or awkward locations so that a bead produced by expressed contents of the tube can be placed upon a target.